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From sweetjonnie <>
Subject Re: ActiveMQ and JNDI provider
Date Tue, 10 Feb 2009 02:26:28 GMT

gregory.guibert wrote:
> Thank you for the link on OpenDS, it looks great and seems to solve half
> my
> problem (alignment of data) :-)
> ...
> When using a file to create an initial context, the file
> looks like this:
> java.naming.factory.initial = com.sun.jndi.ldap.LdapCtxFactory
> java.naming.provider.url=ldap://host1:10389/ou=adminobjects,o=amq,dc=example,dc=com
> The same way ActiveMQ manages the failover mechanism, do you know if it is
> possible to define the OpenDS servers addresses in a single
> file ? I did not find anything about this on the Sun Website.

I think it solved the problem of mutable persistence state accessible by

The alignment of data seems to be more difficult, however. it appears that
you have one LDAP server per Message Queue. At each node, your LDAP server
knows only the JMS Administered Objects associated with that Message Queue.
This is indeed alignment.

The problem with this arrangement is that it appears to require that the
client have understanding of the correct LDAP server to direct requests
against (the same one that is associated with the "current" ActiveMQ
server). If the client can know this, then it doesn't appear to be a
problem. But, I don't believe that the client can know this. If this is
correct, then this is where we lose alignment.

Provided that your code can know of the current ActiveMQ server (preferably
in an event based fashion), then this piece of code can always request the
JMS Administered Objects from the LDAP server (or ActiveMQ JNDI server)
associated with the current ActiveMQ server and rebind these objects in yet
another LDAP server (one that is situated "in front" of the others and to
which all client requests are directed). Unfortunately, you still have a
window between the the time when the "switch" from the last current MQ to
the new current MQ occurs and the repopulation of the client facing LDAP
server occurs. It is within this window that bad things can happen.

I wanted to discuss this with you as much as possible because it is
interesting, but I am afraid that I don't know nearly enough about fail-over
to really add anything. Certainly, I welcome additional notes concerning
this experiment.

jonnie savell
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